Field
This application relates generally to wireless communication and more specifically, but not exclusively, to adapting handover parameters at an access terminal.
Introduction
A wireless communication network provides various types of service (e.g., voice, data, multimedia services, etc.) to users within the coverage area of the network. In some types of networks, access points are distributed throughout a geographical area to provide wireless connectivity for access terminals that are operating within that geographical area. In general, at a given point in time, an access terminal will be served by a given one of these access points. As the access terminal roams throughout the geographical area, the access terminal may move away from its serving access point and move closer to another access point. In addition, signal conditions within a given area may change over time (e.g., due to fading and/or interference), whereby an access terminal may be better served by another access point. In these cases, to maintain mobility for the access terminal, the access terminal may be handed-over from its serving access point to the other so-called target access point.
Ideally, handover occurs in a seamless and reliable manner. In practice, however, various issues may arise during handover.
As one example, an access terminal at a handover boundary between two access points may be frequently handed-over between the two access points. For example, the signal quality seen by the access terminal at this boundary may fluctuate due to fading or other signal conditions. Consequently, at one point in time, the access terminal determines that a second access point provides better signal quality than a first access point and, as a result, initiates handover from the first access point to the second access point. When signal conditions change a short time later, the access terminal determines that the first access point provides better signal quality than the second access point and initiates handover back to the first access point. When signal conditions change again, the access terminal initiates handover back to the second access point, and so on. This condition may be referred to as frequent handover (FHO).
As another example, after handover of an access terminal from a first access point to a second access point is commenced (e.g., due to deterioration of the link between the first access point and the access terminal) but before the handover is completed, the link between the access terminal and the first access point may fail (e.g., due to further deterioration of the link). This condition may be referred to as too-late handover (TLHO) since, in some aspects, the access terminal should have been handed-over to the second access point sooner (i.e., before the link to the first access point failed).
As yet another example, shortly after handover of an access terminal from a first access point to a second access point, the link between the access terminal and the second access point may fail (e.g., due to a poor link between the second access point and the access terminal). This condition may be referred to as too-early handover (TEHO) since, in some aspects, the access point should not have been handed-over to the second access point because the second access point could not yet provide sufficient service for the access terminal.
In conventional wireless networks such a cellular networks, handover is controlled by the network (e.g., by the core network and/or the access points). Consequently, handover problems such as FHO, TLHO, and TEHO are addressed by the core network. For example, a core network entity detects handover problems and defines the parameters used for handover to reduce the handover problems.